Tamper is a common term for a tamping device that precompacts laying material and is part of the standard equipment of a screed of a road finishing machine. The screed comprises a basic screed and optionally extendable screeds that can be extended at the basic screed for changing the working width, and optionally screed broadening parts attached as required. Each of these components of the screed comprises at least one tamper with a separate drive motor, typically a speed-controlled hydraulic motor. The tamper either acts alone in the screed for precompacting, or it acts in combination with an unbalanced mass vibration generator which generates unbalance pulses at the screed plate contributing to the precompacting.